1. Field of the Invention
This disclosure relates to a transmitter having a slew rate control function, and an interface device and a car mounted communication system using the transmitter.
2. Description of Related Art
FIG. 6 is a circuit diagram showing a transmitter having a slew rate control function in accordance with the related art. With respect to the transmitter in accordance with the related art, a switching controller 306 operates in response to a rising edge of an input signal IN, and turns ON a switch 301 and turns OFF a switch 302. According to thus switching control, a charge current I1 (a current value=+I) flows into a capacitor 305 (a capacitance=C) from a constant current source 303 via the switch 301. As a result, a voltage value of an output signal OUT derived from one end (high potential side) of the capacitor 305, begins to rise at a constant slew rate SR1 (SR1=+I/C[V/S]) in response to a current value of the charge current I1 and a capacitance of the capacitor 305.
The switching controller 306 turns OFF the switch 301 when a voltage value of the output signal OUT reaches to a reference voltage Vref. As a result of thus switching control, an output voltage VOUT is maintained approximately same as the reference voltage Vref by the capacitor 305.
The switching controller 306 turns OFF the switch 301 and turns ON the switch 302 in response to a falling edge of the input signal IN. As a result of this switching control, a discharge current I2 (a current value=−I) is provided from the capacitor 305 to a constant current source 304 via the switch 302. As a result, a voltage value of the output signal OUT begins to fall at a constant slew rate SR2 (SR2=−I/C [V/S]) in response to a current value of the discharge current I2 and a capacitance of the capacitor 305.
A related technique of a car mounted communication system is disclosed in Japanese patent publication No. 2009-202720.